Brazil's ex-president Luiz Inacio Lula da Silva says he has "nothing to fear" after being briefly detained by police for questioning over corruption claims.

Police on Friday raided Lula's home in Sao Paulo and spoke to him for three hours about a multi-billion dollar scandal involving the national oil giant Petrobras.

"If they wanted to hear from me, they only had to call and I would have gone, because I owe nothing to anyone and fear nothing," Lula said at a news conference in his first remarks since being released from police custody. 

Lula, 70, said the decision to detain him at his house and take him to a police station for questioning showed "lack of democratic respect" and "judicial authoritarianism". 

"It would have been so simple to invite me to testify. (The judge) did not need to send police to my house and the house of my sons," he said.

"They preferred to show power, arrogance, to make a show."

Earlier on Friday, Federal police officer Jose Cyrispiniano said police also searched offices linked to Lula, including the Instituto Lula, his non-profit organisation, as well as houses of his family members.

Cyrispiniano said that police were acting on a warrant that requires Lula to answer their inquiries as part of an investigation dubbed Operation Car Wash.

Prosecutors clarified that Lula was not arrested, but was held for questioning.

Officials said that a major sweep, including detentions and searches of properties, had taken place in three states as police deepened their investigation into a vast embezzlement and bribery conspiracy centred on Petrobras.

"About 200 federal police and 30 auditors served 44 warrants, including 33 warrants for search and seizure and 11 for detention for questioning," the federal police said. 

Al Jazeera's Marga Ortigas, reporting from Rio de Janeiro, said clashes erupted between groups of rival protesters outside Lula's home in Sao Paulo, following his detention.

Our correspondent said police operation were carried out in three states, in what she described as "the most politically explosive development" in the corruption investigation.  

Da Silva, who served as president from 2003 to 2011, remains a popular figure in the country [The Associated Press]

Jose Chrispiniano, a spokesman for Lula and his institute, said on Friday that the ex-president's detention for questioning and the search of his home amounted to an attack on the rule of law.

"The violence carried out today against the ex-President Lula and his family ... is an assault against the rule of law that impacts all of Brazilian society," he said.

In particular focus of the investigation is a luxury seaside apartment and a country house that prosecutors said they believe were given to him as bribes. Lula said the properties did not belong to him.

In July last year, police launched a major investigation into allegations that the former president had used his connections overseas to benefit Latin America's largest engineering firm Odebrecht.

Lula served as Brazil's president from 2003 to 2011. He remains one of Brazil's most influential figures and his fate is closely linked to that of his successor, President Dilma Rousseff, and the future of the ruling Workers' Party. Rousseff is also facing threats of an impeachment by the opposition-controlled Congress.

Source: Agencies